1. Field of the Invention
The present invention relates to a defect inspection system which inspects a defect such as a particle in an object under inspection, and particularly to a defect inspection system suitable for inspection process of a substrate with a pattern, such as a semiconductor wafer, liquid crystal display, and the like.
2. Description of the Related Art
If particles are present on the surface of a substrate in the process of manufacturing a semiconductor device, liquid crystal display, or the like, failures such as short circuit and inferior insulation will take place therein. Causes by which particles are generated include dust that occurs from equipment, the human body, and process gas and other materials.
With the increasing miniaturization in semiconductor process, the minuteness of a defect that will cause failures is also remarkable and accordingly defect detection with higher accuracy is requested.
Recent years have seen a trend of an increase in the use of multilayer wafers because of higher integration of semiconductors. A multilayer wafer is manufactured by repeating a process of forming a transparent thin film such as an oxide film on a substrate and a process of forming a circuit pattern on the film. For this reason, the need for detection of particles and defects on the surface of the transparent thin film has been important in the field of defect inspection on a wafer.
In order to meet this demand, JP-A-2007-107960 discloses a technique for reducing scattered light from a transparent thin film base pattern using a low-elevation-angle detector in addition to a detector installed in a direction perpendicular to the wafer, used in common dark-field inspection systems, to thereby improve the detection sensitivity.
Likewise, JP-A-2007-33433 also discloses a detection technique using a low-elevation angle as detection angle to reduce unevenness in brightness of scattered light from a wafer.
With the above-mentioned techniques, both a low-elevation-angle detector and a perpendicular detector can be used at the same time, thus enabling defect detection with high sensitivity using a plurality of defect signals.